Unless otherwise indicated herein, the description provided in this section is not prior art to the claims and is not admitted to be prior art by inclusion in this section.
Motor-driven vehicles generally include an engine with a transmission for driving the wheels of the engine. The engine typically transfers power to the transmission via a flywheel attached to one end of a crankshaft, with the flywheel being coupled to a torque converter of the transmission. By convention, the side of the engine at which the crankshaft couples to the transmission is referred to as the rear side or rear end of the engine.
Often, the engine has a significant excess of power available to drive auxiliary systems that are required to perform the vehicle's intended services. A power take-off (PTO) system typically delivers torque from the engine to an auxiliary system component by using the rotation of the crankshaft to rotate a shaft of a component of the auxiliary system, such as a pump or a generator. A PTO system can receive power from the engine in any one of several ways. By way of example, a PTO system could be driven directly by the crankshaft, by a separate shaft coupled to the crankshaft or the transmission, or by gears within the transmission. In any one of these examples, the PTO system could be gear-driven, chain-driven, or belt-driven.
A PTO system can be connected or coupled to the engine in one of several ways. A “rear-drive PTO system” may act as a load driven by the crankshaft via the flywheel, either by a direct connection to the flywheel or by an indirect connection (e.g., via the transmission). Because high-power PTO systems are typically bulky, implementing such a rear-drive PTO system is not always practical. For instance, an engine compartment may not be sufficiently large enough to accommodate a rear-drive PTO system. The gearing of a vehicle's transmission may also make it impractical to use the transmission to drive the rear-drive PTO system, as the transmission may not be able to deliver the requisite torque to both the wheels and the PTO system.
Another type of PTO system is a front-drive PTO system, which may be mounted to the front end of the engine and coupled to the crankshaft at the nose of the crankshaft. By convention, the nose of the crankshaft is the end of the crankshaft opposite the end of the crankshaft at which the flywheel is attached. Such a system may also be bulky, however, and is typically an integral part of the engine's crankcase. One disadvantage of integral PTO system is that performing maintenance on the PTO system requires taking the vehicle out of service, sometimes for an extended period of time. At a minimum, the engine oil must be drained prior to doing any type of maintenance on the PTO system, and the engine, and likely the vehicle, will remain out of service until the PTO system is able to be restored.
Further, to provide lubrication for PTO system components, a front-drive PTO system is usually connected to the engine's oil sump. There is thus a possibility that combustion debris can enter the PTO system's oil bath, thereby fouling PTO system components and possibly shortening the service life of such components. In the same vein, wear products from both systems can enter the oil sump, which may also degrade the performance and the service life of PTO system components as well as engine components.